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Background: RAT are essential to identify SARS-CoV-2-positive patients, isolate them, break the transmission chain, and contain COVID-19. However, rapid antigen tests (RATs) have low sensitivity, which can lead to missed cases. This study evaluated the effectiveness of a RAT kit with reference to the gold standard real-time RT-PCR for suspected COVID-19 patients.
Methods: We investigated 370 nasopharyngeal swabs at MTI, Khyber Teaching Hospital Peshawar, Pakistan for RAT and the real-time RT-qPCR. We evaluated the effectiveness of the RAT by determining its sensitivity, specificity, PPV (positive predictive value), NPV (negative predictive value), diagnostic accuracy and kappa statistics.
Results: The results indicated a sensitivity of 79.35% and a specificity of 98.6%. The PPV was 97.62% and the NPV was 86.89%. The accuracy between the two techniques was found to be 90.54% with a kappa coefficient of 0.800. We identified that at lower cycle threshold (CT) values, the RAT was more sensitive. However, at higher CT values, the rapid antigen test sensitivity decreased.
Conclusion: The RAT had a high specificity but its sensitivity become low with high CT values and low viral load, thus it was more likely to miss some positives cases. Our findings suggest that the rapid antigen test can be a beneficial tool in mass screening of COVID-19, particularly in settings where RT-PCR is not feasible due to resource constraints or turnaround time but it is important to be aware of its limitations.
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